1. Field of the Invention
The present invention relates to an electronic balance including a balance housing and a measuring cell for electromagnetic load compensation. The measuring cell is placed in the balance housing and is separated by means of a partition from the electric circuits of the electronic analyzing and indicating means. The balance further includes a load receiving member with a receiving cone for the weighing dish extending through an opening in the balance housing. The balance also includes control elements.
2. Description of the Prior Art
In high-resolution balances, even small air movements within the balance influence the measurement results. The reasons of such air movements within the balance housing are the different pattern of heating of the individual electric and mechanical components and the influence of heat radiation acting on only one side from the inside and from the outside, as well as cold air flows as they occur during winter when the windows are open. The different heating or cooling of the individual balance components not only results in air movements, but it also results, due to different longitudinal expansions of individual components, for example, in a change of the length of the levers and, thus, in a change of the transmission ratios of the forces to be transferred and transmitted by the levers.
A balance of the above-described type is known from Swiss Pat. No. 638,894 corresponding to U.S. Pat. No. 4,280,577. The Swiss patent proposes in the above-described type of balance to make individual components hollow, for example, the coupling member of the load receiving member, and to accommodate the elastic bearing in the hollow component, in order to obtain a uniform expansion of these two components as a result of a uniform temperature pattern.
The Swiss patent proposes as another feature to separate with respect to space the measuring cell and the electronic analyzing and indicating circuitry by means of a partition.
By means of this partition, it is possible to improve the temperature-related behavior of the balance and, thus, to achieve a more uniform longitudinal expansion of some of the mechanical components. However, air movements which negatively influence the weighing result and are caused by non-uniform heating cannot be avoided by the measures proposed by the Swiss patent to such an extent that the consequences of the air movements could be eliminated in high-resolution balances. Air will always penetrate through the gaps between the lower portion and the upper portion of the housing to such an extent that an air flow is generated which escapes especially through the gap surrounding the receiving cone for the weighing dish.
It is, therefore, the primary object of the present invention to provide an electronic balance in which the above-described disadvantages are avoided.
Specifically, it is the object of the present invention to provide an analytical balance in which a uniform pattern of heating of the sensitive balance components prevents the formation of air flow and of non-uniform expansion of mechanical components.